Generic thermoelectric systems take advantage of the Seebeck, Peltier and/or Thomson effects and may therefore be constructed as thermoelectric generators, which supply an electric current when arranged in a thermal gradient or as Peltier elements, which cool or generate heat when supplied with electrical energy. In order to be able to use these slight effects occurring at each thermocouple efficiently, a plurality of thermocouples is preferably connected in series.
For example, a so-called thermoelement or thermoelectric system comprising a plurality of thermocouple elements connected in series is known from DE 101 22 679 A1. Here, the thermocouples are applied to a substrate, for example a film. In the process, separate portions comprising thermoelectrically active materials with different Seebeck coefficients are arranged alternately in a plate-like manner next to each other and distanced from one another by means of webs or in a wavelike manner between two layers such as layers of clothing with different temperatures. Because of the large spaces between the strips of the individual thermoelectrically active materials or in the wavelike structure, between the waves, the effectiveness of the thermoelement falls. Furthermore, the thermoelectrically active materials are not insulated from one another so that a further convergence of the thermocouples is not possible due to the risk of short circuits alone. Finally, the thermoelement is not inherently rigid due to the thin-film substrate materials used such that in applications where inherent rigidness is required, an additional support structure is necessary.
A similarly constructed thermoelectric system is presented by Weber et al. (J. Weber, K. Potje-Kamloth, F. Haase, P. Detemple, F. Voelklein, T. Doll, “Coin-size coiled-up polymer foil thermoelectric power generator for wearable electronics”, Sensors and Actuators, 132 (2006) 325-330). To produce this system, metal films were sputtered onto a polyamide foil, which was then wound up into a coil. This winding makes it possible to produce a series connection in continuous form, the thermoelectrically active materials being insulated from one another due to the winding. The problem with this is the wavelike structure of the thermoelectrically active materials in relation to each other, because unused intermediate spaces emerge as a result, which can lead to parasitic heat flow. Optimum use of the whole substrate surface by the thermocouples would be desirable instead.
Willfahrt et al. describe a method for printing thermoelectric generators (TEG) (A. Willfahrt, G. Huebner, E. Steiner, X. Crispin “Screen printed thermoelectric generator in a five layers vertical setup”, Proceedings of Large-Area, Organic and Polymer Electronics Convention 28-30.06.2011 (LOPE-C 11), June 2011, Frankfurt/M., ISBN 978-3-00-034957-7). For this purpose, thermoelectrically different materials are printed in thin layers onto a flat substrate out of which strips are subsequently cut, which are stacked on top of one another and connected to one another in series with switched clamps. This subsequent connection is only possible in an industrial process at great expense, so the method is of no commercial interest. Moreover, the wavelike structure of the thermocouples has intermediate spaces which lead to the problems already referred to above.
FR 2 620 573 A1 discloses a concertina-like folded thermoelectric system comprising a plurality of thermocouples and a method for producing said system. In this method, the different thermoelectrically active materials are applied in long parallel strips to an insulating substrate, which in the next step is covered in a further insulating layer and folded in a meandering shape along the parallel strips. This results in a thermoelectric system, which although it uses the entire surface substrate with thermoelectrically active materials, the additional insulating coating makes the production process more complicated and an additional layer is obtained in the resulting folded thermoelectric system, which can lead to parasitic heat flow. Furthermore, the method described in FR 2 620 573 A1 has disadvantages if a batch print process is used for the coating since the number of thermocouples is limited to how many can be printed in one direction.
A folded thermoelectric generator emerges from CH 413 018 A, in which the thermoelements, which are folded in zigzag form, are produced by applying alternate strips of materials with different thermoelectric potentials onto a non-electrically conductive film base.
WO 2005 117 154 A1 discloses a thermoelectric semiconductor module, which is produced by a printing process or depositing under vacuum, thin p-type and n-type layers being applied lengthwise to a flexible thin layer in an alternating manner. The thermoelectric modules are either folded into a coil or a zigzag.